…and a Jetpack
Besides not being evil, the other thing that set most of the Autobots apart from the Decepticons was they lacked the ability to fly. The solution to that problem was to give Optimus Prime a jetpack in the cartoon (borrowed from Sideswipe) which temporarily let him take to the skies. The Lego version includes no flying capabilities, but it does help cover up some of the exposed hinges and other components on the back of Optimus that let him transform.
